Changing values(parameteres) in input text file at a certain line

MATErial,1

SOLId

PLANe STRAin

ELAStic ISOTropic 1000.0 0.25

! Blank termination record

COORdinates

1 0 0.0 0.0

2 0 4.0 0.0

3 0 10.0 0.0

4 0 0.0 4.5

5 0 5.5 5.5

6 0 10.0 5.0

7 0 0.0 10.0

8 0 4.2 10.0

9 0 10.0 10.0

! Blank termination record

ELEMents

1 1 1 1 2 5 4

2 1 1 2 3 6 5............................

The text file looks like this. I want to change the fourth line last two parameters 1000.0 and 0.25 to user defined input parameters and run the system command to execute the input text file in external program. Any help could you greatly appreciated. Thanks in advance

Answer 1

[Raunak Gupta]

Hi,

You can use textscan while reading specific line from the text file and in this case it’s the 4th line. Since there is some initial whitespaces in the 4th line which will go after reading from textscan I have added a tab character which compensates for same.

The following code may help you achieved the same.

1. Reading 4th line and creating the changed version based on userInput1 and userInput2.
2. Writing all the lines in a new file with changed 4th line.

userInput1 = 50; % User Input 1
userInput2 = 0.5; % User Input 2
% Original File
fid=fopen('check_nf.txt','r');
linenum = 4;
C = textscan(fid,'%s',1,'delimiter','\n', 'headerlines',linenum-1);
line_4_words = strsplit(string(C{1}));
line_4_words(3) = num2str(userInput1);
line_4_words(4) = num2str(userInput2);
changedLine = sprintf('\t') + join(line_4_words) + newline;
fclose(fid);
count = 1;
fid=fopen('check_nf.txt','r');
% New File
fod=fopen('new_nf.txt','w');
while ~feof(fid)
  if count == 4
    fprintf(fod,'%s',changedLine);
    fgets(fid);
  else 
    fprintf(fod,'%s',fgets(fid));
  end
  count = count + 1;
end
fclose(fod);
fclose(fid);

[RAKESH KUMAR TOTA]

Thanks a lot Raunak Gupta.. It really saved lot of time.

What if i dont know which line is that to enter input file ? Here i know i have to edit in 4th line. how to generalize it. Next to write in the same input file what is the command.

[RAKESH KUMAR TOTA]

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